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Mass oyster mortality occurred at an oyster farm in the Setiu Lagoon on the east coast of Peninsular Malaysia in December 2023. According to interviews with aquaculture farmers, heavy rains that occurred from 20 November to early December caused flooding in the surrounding area, leaving it exposed to low-salinity water for a long period. Mass mortality occurred at oyster farms in early December, with farmers estimating that the dead oysters had a shell length of 1–5 cm and mortality rate of over 90%, and that approximately 50,000 oysters had died. An analysis of meteorological data indicated that a monthly rainfall value of more than 1200 mm/month, which is more than double the normal amount, was observed in November in the same region. During the same period, the seawater temperature in the South China Sea was 1°C higher than normal, and the northeast monsoon caused winds from the northeast to transport moist air to the eastern coast of Peninsular Malaysia, causing heavy rain. Currently, only one waterway, approximately 200 m wide, connects the lagoon to the sea. Until approximately 2012, two waterways were connected to the sea. We concluded that by increasing the number of channels to two, the decrease in salinity in the lagoon during the rainy season could be reduced by enhancing phytoplankton occurrence.

Ulva green tides have adversely affected coastal ecosystems. In June 2023 in Changhua County, Taiwan, an unprecedented floating tubular Ulva bloom spanning about 30 km of coastline caused about 30 % reduction in oyster yield as reported by local farmers. Understanding its taxonomic and ecological basis is crucial for preemptive and remedial measures. Based on molecular (rbcL and tufA) and morphological evidence, Ulva meridionalis was the cause of this green tide. Haplotype network analysis (based on ITS) suggests that this green tide originated from northern China via the China Coastal Current. Historical survey data indicate that U. meridionalis arrived in Taoyuan Algal Reef (about 150 km north of the bloom area) as far back as 2018. Our ecophysiological experiments revealed that U. meridionalis exhibited a rapid daily growth rate with biomass increment up to 13–21 % when subjected to local nutrient-rich waters under lower salinity and spring-like conditions. Although historical ecological and poultry/livestock data analyses showed no noticeable change in sea surface temperature and rainfall over the past decade, a gradual rise in agricultural nitrogen and phosphorus output was observed. This taxonomic and ecological background lays the groundwork for long-term ecological monitoring. Moreover, this study exemplifies the detrimental impact of an unforeseen Ulva bloom on oyster farming. [ABSTRACT FROM AUTHOR]

Ostrea chilensis (a flat oyster) is native to Chile and New Zealand. In Chile, this oyster has been cultured and harvested for at least 80 years. However, the culture of flat oysters has not developed like other aquaculture activities in Chile, mainly due to the inefficiency of the collectors (made of ribbed mussel shells) and the lack of spats produced. The objective of this study was to determine the capacity of spat collectors for the settlement of O. chilensis. For this purpose, field and laboratory experiments were carried out. Our results indicated that oyster larvae do not have a preference for either side of the shell (periostracum or nacreous) to settle on. However, after one year of growth in the field, juveniles were more abundant on the nacreous side of the shell (spat collector). Also, the oysters that settled on the nacreous side of the valve were larger. This was due to the fact that the periostracum had a greater number of epibionts, and they competed for space and resources with the settled oyster spats, causing a decrease in the abundance of oyster spats on that surface. Our findings raise the possibility that collectors could improve efficiency in the production of spats. Finally, we discuss the implications of these results for the Chilean oyster-farming industry. [ABSTRACT FROM AUTHOR]

Nonlinear regression modeling was used to study the nursery production of the oyster Crassostrea virginica in the Celestún (CL) and Rio Lagartos (RL) lagoons in Yucatán, Mexico. Relationships between production parameters and environmental variables were also established. Spat (2.40 ± 0.20 mm) was obtained from a hatchery and reared in Nestier- type trays using an off-bottom system. Oyster cultivation took place from May 2021 to September 2021 and ended after 122--126 days when oysters reached 30.00 mm. There were no significant differences in final height (CL: 30.80 ± 0.42 mm; RL: 31.80 ± 0.65 mm; P = 0.18) and growth rate (CL: 0.23 ± 0.02 mm·d-1; RL: 0.23 ± 0.01 mm·d-1; P = 0.98). Final survival was 71.45% in CL and 99.40% in RL. Nonlinear regression curves were statistically satisfactory for analyzing growth and survival. Salinity (CL: 15.23 ppt; RL: 35.02 ppt), temperature (CL: 29.64 °C; RL: 31.02 °C), dissolved oxygen (CL: 4.50 mg· L-1; RL: 5.04 mg· L-1), pH (CL: 8.10; RL: 8.34), chlorophyll a (Chl a) (CL: 3.23 mg·m--3; RL: 6.85 mg·m--3), and total dissolved solids (CL: 16,101 mg·L-1; RL: 34,838 mg·L-1) were significantly higher in RL (P < 0.05). Except for Chl a, the environmental variables were more stable in RL than in CL (P < 0.05). In RL, the growth rate was positively related to salinity and pH. In CL, the growth rate slowed when salinity decreased, and the mortality rate diminished when salinity, dissolved oxygen, and total dissolved solids increased and pH decreased. Salinity was mainly responsible for the observed differences in production between lagoons. Even when temperature and salinity were high in RL, acceptable growth rate and survival were observed, possibly due to stable rearing conditions. [ABSTRACT FROM AUTHOR]

Abstract In this study, we aimed to evaluate the synergistic effect between the Amazon seasonality and the El Niño climate anomaly (2015/16 event) on the growth of oysters cultivated on the Amazon coast in comparison with the growth of oysters in a normal year (2013). It should be noted that both experiments determined the absolute growth of oysters Crassostrea gasar by reading microgrowth using an internal calcein marker. the results clearly indicate the synergistic effect of the Amazon seasonality with the El Niño climatic anomaly. thus, in normal years, the best oyster growth performance occurs in the dry season, while in El Niño years it occurs in the wet season. This is the first study carried out in the Amazon region that aims to analyze the effects of El Niño on the production of fishery resources from aquaculture. Such information enables adaptations in the planning of the production cycle of oyster farming, serving as an investment indicator.

Plastic materials are widely used for automotive parts, electronic devices, and faucet parts because they are lighter than metals and have superior workability and productivity. However, due to their poor weather resistance, their surfaces must be painted or plated. As a pretreatment for plating, it is most important to roughen the surface to obtain strong adhesion through an anchor effect. The conventional method is to use chemicals, but the use of chemicals is now severely restricted by the REACH regulation in the EU due to the environmental impact of wastewater and effluent treatment. We have obtained the same or higher adhesion strength than conventional methods by using a pretreatment method with ozone fine bubbles, which has almost no environmental damages. [ABSTRACT FROM AUTHOR]

Ostrea chilensis (a flat oyster) is native to Chile and New Zealand. In Chile, this oyster has been cultured and harvested for at least 80 years. However, the culture of flat oysters has not developed like other aquaculture activities in Chile, mainly due to the inefficiency of the collectors (made of ribbed mussel shells) and the lack of spats produced. The objective of this study was to determine the capacity of spat collectors for the settlement of O. chilensis. For this purpose, field and laboratory experiments were carried out. Our results indicated that oyster larvae do not have a preference for either side of the shell (periostracum or nacreous) to settle on. However, after one year of growth in the field, juveniles were more abundant on the nacreous side of the shell (spat collector). Also, the oysters that settled on the nacreous side of the valve were larger. This was due to the fact that the periostracum had a greater number of epibionts, and they competed for space and resources with the settled oyster spats, causing a decrease in the abundance of oyster spats on that surface. Our findings raise the possibility that collectors could improve efficiency in the production of spats. Finally, we discuss the implications of these results for the Chilean oyster-farming industry.

Non-indigenous seaweed species have been introduced to the coasts of Brittany, France for decades, with an increasing arrival rate since the 1970s due to both the introduction of the Pacific oyster and increased maritime traffic. In this study, seven species of red macroalgae originating from the Pacific Ocean were found in new locations around the coasts of Brittany between 2018 and 2022. The seaweed species belong to four different orders: Ceramiales (Antithamnion hubbsii, Polysiphonia morrowii, and Symphyocladiella dendroidea), Halymeniales (including Pachymeniopsis lanceolata and Polyopes lancifolius), Rhodymeniales (Botryocladia wrightii), and Gigartinales (Solieria sp.). The dispersal mode and putative invasive potential of each species were examined, and the species were described in terms of their macroscopic and microscopic appearance and habitat. These finds result from a combination of citizen science and long-term monitoring. Used together, these two approaches can aid in the detection of these species on other European coasts and in understanding their dispersion. [ABSTRACT FROM AUTHOR]

The Pacific oyster Crassostrea gigas is one of the world's most cultivated and prized molluscs. Although it is usually considered a luxury product, it meets all the requirements to be included in a sustainable diet, and its production and consumption have great potential for growth in the coming years. Oyster farming is a worldwide activity, with China and France as the main producers, but recently, the possibility of implementing the Italian production, mainly focused on clams and mussels, has been considered an interesting issue, especially due to the growing local and global demand. The present study has been carried out by collecting data from the Sacca di Goro, north-east Italy, the most important national mollusc farming area. Life cycle assessment (LCA) methodology was applied to two different farming scenarios in order to improve the overall sustainability of the process. Using OpenLCA™ software (GreenDelta, Berlin, Germany) and the ReCiPe® midpoint (H) v.1.12 method, the environmental impacts of the traditional Italian farming technique, carried out entirely offshore in longlines, and the alternative option, in which the oyster seed pre-fattening phase was carried out in the lagoon, were calculated and compared. The results show that replacing the current pre-fattening phase with pre-fattening in a lagoon reduces CO2 emissions by approximately 12% and all other impact categories by approximately 9%. In addition, non-recyclable plastic materials and fuel consumption emerged as the main environmental hotspots. [ABSTRACT FROM AUTHOR]

Although Crassostrea nippona and C. gigas are occasionally found to be sympatric, little is known about the differences in tolerance against environmental stresses between species, which may potentially result in severe economic losses due to the neglect of species-specific biological characteristics in farming practices. Therefore, two independent and consecutive experiments were performed to evaluate the differences in temperature and salinity tolerance between C. nippona and C. gigas spat and determine the optimal environmental conditions for the aquaculture of C. nippona spat. The experimental results of dynamic treatment showed that the accumulative survival rate (ASR) of C. nippona spat was generally lower than that of C. gigas throughout temperature changes and salinity decreases, while the ASR of C. nippona spat was superior to that of C. gigas with increasing salinity. In addition, the daily growth rate (DGR) of both species was significantly inhibited at 18 °C and peaked at 25 °C with increasing temperature (p < 0.05) at each experimental salinity. At 32 °C, the survival rate (SR) of C. nippona spat was significantly lower than that of C. gigas on day 10 at all salinities tested (p < 0.05), whereas the difference in the SR between species at 35 psu gradually disappeared with prolonged stress time. The data indicated that C. gigas spat was suitable for rearing at temperatures of 25 and 32 °C at all salinity levels, except the combination of 32 °C and 35 psu. By contrast, combinations of 25 °C and salinities of 21–35 psu were considered as the optimal environmental conditions for the long-term culture of C. nippona spat. These present findings contribute to a better understanding of the tolerance of C. nippona spat to environmental stresses and suggest that particular attention should be paid to the inferior adaptability of C. nippona when farming in locations outside their natural habitats. [ABSTRACT FROM AUTHOR]

Coastal erosion in the lagoon systems is concerned as they are dynamic landscapes, often highly productive and beneficial to humankind. Cigu Lagoon contains rich and diverse ecosystems ranging from mangroves to salt fields, and from fish to birds (e.g., endangered black-faced spoonbill). As well as forming part of the country’s natural defenses against typhoons and storm surges, it is also economically important for oyster farming, fish-pond aquaculture and ecotourism. However, with the construction of reservoir, fishery harbors and breakwaters, sediment transport decreases and sand barrier islands have eroded, narrowed, lowered and moved landwards. Cigu is a rural area with decreasing, aging population, becoming a “super-aged society” as defined by World Health Organization. Therefore, it is imperative to study the socioeconomic impacts of these changes, and then to explore critical adaptation factors and potential adaptation strategies. In this research, we conducted interviews and a fuzzy analytic hierarchy process survey. Diverse stakeholders were identified and mapped using a stakeholder rainbow diagram and a power–interest grid. The results show that stakeholders consider the economy to be the most important adaptation factor, especially in relation to the employment opportunities. There are some forms of livelihood diversification in Cigu. Collaboration among young entrepreneurs is the key to socioeconomic adaptation. These factors and strategies may foster socioeconomic adaptation to coastal erosion or geomorphological change, to be aggravated by climate change and other stressors.

Oysters are one of the main aquatic products produced in Taiwan. However, because of the gradual changes in the environment of the Waisanding Sandbar, the oyster farming environment along the coast of Chiayi is shrinking, leading to greater operational risk and uncertainty. This study adopted a three-stage method to investigate the socioeconomic uncertainty that fishing communities face regarding environmental changes and to understand the environmental risk and fishery management awareness of different stakeholders as well as their views on adaptation strategies. In-depth interviews were used in the first stage. In Stage 2, two-round focus group interviews were conducted to organize views on the environment and climate, the oyster industry and management, and adaptation strategies. In the final stage, the AHP method was adopted to analyze the opinions of different stakeholders. The results showed factors affecting environmental change, oyster industry, and management among different stakeholders as well as the cognitive differences within the corresponding adaptation strategies. Therefore, socioeconomic and ecology complexities and uncertainties should be considered for enhancing social capital and promoting risk communication, more diverse social–ecological system data to assist fishery governance, and oyster industry development and adaptation strategies. [ABSTRACT FROM AUTHOR]

[Display omitted] • Tubular bamboo charcoal with different lengths is used as anode material in SMFC. • Long bamboo anodes show better bioelectricity production and sediment remediation. • SMFC-A6 achieves the highest maximum power density, four times higher than SMFC-A3. • Long tubular bamboo anodes support the reduction of COD concentration. • Long bamboo anodes improve sediment ORP and bioelectricity generation of SMFC. The amount of electricity generated depends on electron transfer, so the length of anode as electrode could be the determining factor for improving the performance of sediment microbial fuel cells (SMFC). In this study, tubular bamboo biochar with different lengths, namely SMFC-A3 (3 cm), SMFC-A6 (6 cm) and SMFC-A9 (9 cm), were used as anode material to reduce cost and carbon footprint in SMFC. We investigated the bioelectricity generation and anoxic sediment remediation from oyster farm of Tongyeong City, South Korea through SMFC system. Tubular bamboo biochar was characterized by elemental analysis (elemental composition), FESEM (morphology), TGA (weight loss) and XRD (crystalline framework). It was found that SMFC performance increased with increasing length of anode to improve the quality of anaerobic sediment (p < 0.05). SMFC-A6 generated the highest voltage of 50 mV among all cases. Polarization curves showed that SMFC-A6 achieved the highest maximum power density of 0.060 mW/m2, with a fourfold and a onefold increase compared to SMFC-A3 and SMFC-A9, respectively. In SMFC-A9, increase in redox potential and decrease in chemical oxygen demand (COD) was observed (−197 mV, 11 mg/L), compared to control case with sediment only (−240 mV, 25 mg/L). Removal efficiency of COD in SMFC-A9 and SMFC-A6 was 67 % and 61 % higher than that in SMFC-A3 (48 %). The result of the study could provide a simple strategy for coastal sediment remediation while generating bioelectricity. [ABSTRACT FROM AUTHOR]

Abstract Due to the competition for food, space, oxygen and due to their role as diseases vector, epibionts can negatively affect oyster farming. We assessed the efficacy of six methods commonly used for the removal of epibionts from oyster shells during farming. The experiment was conducted at an oyster farm on the Paraná coast – South Brazil. Oysters (Crassostrea gasar) were acclimated for 90 d in the cultivation system and later exposed to cleaning treatments: i) freshwater; ii) hypersaline water; iii) sodium hypochlorite solution; iv) quaternary ammonia solution; v) exposure to air; vi) hydroblasting; and vii) no cleaning procedure (control). After treatment, oysters were kept in the cultivation system for 15 and 30 d – when the total incrustation and mortality were measured. Epibionts from nine phyla were identified. The most abundant were Arthropoda (Crustacea) (62.5%), Mollusca (33.8%) and Annelida (3.1%). Freshwater [15 (n = 2263 epibionts) and 30 days (n = 2822 epibionts)] and hydroblasting [15 (n = 1850 epibionts) and 30 days (n = 2389 epibionts)] treatments were the most efficient to reduce epibionts and caused lower rates of oyster mortality [15 (5.0 and 3.33%, respectively) and 30 days (1.67 and 6.67%, respectively)].

The Pacific oyster Crassostrea gigas is one of the world’s most cultivated and prized molluscs. Although it is usually considered a luxury product, it meets all the requirements to be included in a sustainable diet, and its production and consumption have great potential for growth in the coming years. Oyster farming is a worldwide activity, with China and France as the main producers, but recently, the possibility of implementing the Italian production, mainly focused on clams and mussels, has been considered an interesting issue, especially due to the growing local and global demand. The present study has been carried out by collecting data from the Sacca di Goro, north-east Italy, the most important national mollusc farming area. Life cycle assessment (LCA) methodology was applied to two different farming scenarios in order to improve the overall sustainability of the process. Using OpenLCA™ software (GreenDelta, Berlin, Germany) and the ReCiPe® midpoint (H) v.1.12 method, the environmental impacts of the traditional Italian farming technique, carried out entirely offshore in longlines, and the alternative option, in which the oyster seed pre-fattening phase was carried out in the lagoon, were calculated and compared. The results show that replacing the current pre-fattening phase with pre-fattening in a lagoon reduces CO2 emissions by approximately 12% and all other impact categories by approximately 9%. In addition, non-recyclable plastic materials and fuel consumption emerged as the main environmental hotspots.

Ocean space is of paramount importance to coastal regions worldwide. However, rapid coastal development has led to competition in marine spatial allocation, exacerbating conflicts within maritime domains. Despite significant progress in establishing regulations for coastal governance in Taiwan, conflicts across diverse maritime industries due to a lack of marine spatial planning (MSP) institutions remain a persistent challenge. Potential conflict areas were identified via geographic information system (GIS) maps to assist maritime governance and used in several rounds of coordination meetings with stakeholders for zoning. A regional MSP framework for improving maritime governance is proposed based on a case study, which shows that even without legal MSP institutions, local or certain central government departments can act as the key authorities for implementing the bottom-up planning concept with strong engagement from local communities. The proposed planning process includes: (1) establishing and employing a monitoring system to promptly identify marine activities that can facilitate efficient enforcement; (2) continuous communication with stakeholders led by the local government to improve amendment regulations and aid compliance; and (3) prioritizing the preservation of traditional use rights with community self-management to accelerate regional MSP processes. • GIS maps assist in identifying conflict-prone areas, aiding stakeholder coordination. • Lacking legal MSP frameworks, local governments facilitate bottom-up planning, engaging communities in maritime governance. • Implementing a monitoring system enhances enforcement efficiency by swiftly identifying various marine activities. • Prioritizing traditional use rights and involving communities in self-management expedites the regional MSP process. [ABSTRACT FROM AUTHOR]

The Santa Catarina Island Bay (SCIB) contributes with the largest production of cultivated oysters in Brazil, which is almost entirely based on hatchery produced cultchless oyster spat, whose metamorphosis is induced by an epinephrine solution. A production scale experiment was carried out to analyze the technical feasibility of the spat-on-shell system in SCIB. The experiment was carried out for 47 weeks, involving an internal phase, the larval settlement, and an external phase, encompassing nursery and growth. Nursery periods varied according to the experimental treatments: T3W - 3 weeks; T5W - 5 weeks; and T12W - 12 weeks. T3W and T5W showed lower survival during the two-week period shortly after transfer of the cultch from the nursery to the grow-out phase, likely linked to premature exposure of the spat in the cultch strings to predators such as fish. The 12-week nursery period showed the best results with clusters with a median of 6 animals and 11.4 g of meat per oyster at the end of the experimental period. Future studies could verify whether longer nursery periods or alternative methods to avoid exposure to predators can outperform these results.

The Pacific oyster (Crassostrea gigas) is an important species in oyster farming worldwide, including in Japan. Hiroshima Bay is one of the most important oyster farming areas in Japan. We investigated the occurrence of antifouling biocides used worldwide including diuron, Irgarol 1051 (Irgarol), and 4,5-dichloro-2-n-octyl-4-isothiazolin-3-one (DCOIT), which have been detected at sub-ppb levels in seawater in Japan, and estimated their no observed effect concentrations (NOECs). In recent years, the spat settlement of Pacific oysters has become poor, which presents a challenge for oyster aquaculture in Hiroshima Bay; hence, we conducted embryotoxicity and larva settlement tests using Pacific oysters. Compared to diuron and Irgarol, DCOIT exhibited a higher toxicity toward oyster embryos, and the minimum 24-h NOEC toxicity value for the oyster embryos was <3 ng/L. The highest concentrations of diuron, Irgarol, and DCOIT in the environmental seawater in the Seto Inland Sea were 27.6, 3.2, and 24 ng/L, respectively. Considering the NOECs, the environmental concentrations of these biocides suggest that the ecological risks posed by diuron and Irgarol are low, whereas those posed by DCOIT are high. However, the rate of detection of DCOIT was low because it degraded rapidly in the seawater before treatment for chemical analysis, except in the case of the treatment on the research vessel. [ABSTRACT FROM AUTHOR]

The Santa Catarina Island Bay (SCIB) contributes with the largest production of cultivated oysters in Brazil, which is almost entirely based on hatchery produced cultchless oyster spat, whose metamorphosis is induced by an epinephrine solution. A production scale experiment was carried out to analyze the technical feasibility of the spat-on-shell system in SCIB. The experiment was carried out for 47 weeks, involving an internal phase, the larval settlement, and an external phase, encompassing nursery and growth. Nursery periods varied according to the experimental treatments: T3W - 3 weeks; T5W - 5 weeks; and T12W - 12 weeks. T3W and T5W showed lower survival during the two-week period shortly after transfer of the cultch from the nursery to the grow-out phase, likely linked to premature exposure of the spat in the cultch strings to predators such as fish. The 12-week nursery period showed the best results with clusters with a median of 6 animals and 11.4 g of meat per oyster at the end of the experimental period. Future studies could verify whether longer nursery periods or alternative methods to avoid exposure to predators can outperform these results. [ABSTRACT FROM AUTHOR]

Although Crassostrea nippona and C. gigas are occasionally found to be sympatric, little is known about the differences in tolerance against environmental stresses between species, which may potentially result in severe economic losses due to the neglect of species-specific biological characteristics in farming practices. Therefore, two independent and consecutive experiments were performed to evaluate the differences in temperature and salinity tolerance between C. nippona and C. gigas spat and determine the optimal environmental conditions for the aquaculture of C. nippona spat. The experimental results of dynamic treatment showed that the accumulative survival rate (ASR) of C. nippona spat was generally lower than that of C. gigas throughout temperature changes and salinity decreases, while the ASR of C. nippona spat was superior to that of C. gigas with increasing salinity. In addition, the daily growth rate (DGR) of both species was significantly inhibited at 18 °C and peaked at 25 °C with increasing temperature (p < 0.05) at each experimental salinity. At 32 °C, the survival rate (SR) of C. nippona spat was significantly lower than that of C. gigas on day 10 at all salinities tested (p < 0.05), whereas the difference in the SR between species at 35 psu gradually disappeared with prolonged stress time. The data indicated that C. gigas spat was suitable for rearing at temperatures of 25 and 32 °C at all salinity levels, except the combination of 32 °C and 35 psu. By contrast, combinations of 25 °C and salinities of 21–35 psu were considered as the optimal environmental conditions for the long-term culture of C. nippona spat. These present findings contribute to a better understanding of the tolerance of C. nippona spat to environmental stresses and suggest that particular attention should be paid to the inferior adaptability of C. nippona when farming in locations outside their natural habitats.

Biosecurity, Crassostrea gigas, epidemiology, ostreid herpesvirus (OsHV-1) var, oyster farming, vertical transmission Keywords: biosecurity; Crassostrea gigas; epidemiology; ostreid herpesvirus (OsHV-1) var; oyster farming; vertical transmission EN biosecurity Crassostrea gigas epidemiology ostreid herpesvirus (OsHV-1) var oyster farming vertical transmission 4012 4017 6 07/21/21 20210801 NES 210801 In recent decades, mortality caused by ostreid herpesvirus (OsHV-1) and a variant (OsHV-1 var) has severely impacted the production of Pacific oyster, I Crassostrea gigas i , chronologically in France, New Zealand (NZ) and Australia (Jenkins et al., 2013; Keeling et al., 2014; Segarra et al., 2010). Case study of vertical transmission of ostreid herpesvirus-1 in Pacific oysters and biosecurity management based on epidemiological data from French, New Zealand and Australian hatchery-propagated seed We have collated data from the production of Pacific oysters across these countries to assess the risk associated with breeding oysters from broodstock grown in OsHV-1 var-infected waters. [Extracted from the article]

Abstract In the last decades the oyster faming stands out as the main mitigating measure to the decline of the fishery, as it presents socio-economic and environmental viability. However, for the success of the activity, it is necessary to understand the stages of cultivation, as well as the growth performance of the species to be cultivated. The present work aims to characterize the growth and survival of Crassostrea tulipa, cultivated on the Amazon coast. For this purpose, oysters were grouped by commercial size class (seed, juvenile, baby, average and masters) and compared the growth rates and their relationships with the abiotic variables. There was no difference in the average growth between the oyster classes, however, when comparing them in the total and percentage growth rates, a higher performance was observed in the oysters classified by juvenile and seed, respectively. The relationship of salinity to oyster growth was evidenced only in the class of juvenile oysters. The cultivation time required to obtain native oysters in the commercial size varied between four and seven months, being inferior to those found in other Brazilian regions.

An increase in oyster aquaculture as a sustainable method of shellfish production is one response to overharvest and degradation of natural oyster reefs over the past century. Successful aquaculture production requires determining the environmental conditions optimal for oyster growth. In this study, the salinity, temperature, chlorophyll a concentration and the growth of Crassostrea virginica were monitored at four locations within the Mission-Aransas Estuary, Texas (USA), a shallow subtropical estuary influenced by relatively low freshwater inflow. Mean growth of the oyster shell (0.205 mm d–1 and 0.203 g d–1) and soft tissues (3.447 mg d–1) was highest when salinity was low (mean = 15.5) and chlorophyll a concentration was high (8.4 μg l–1). Oyster growth also varied temporally with periods of spawning. In low-inflow estuaries such as the Mission-Aransas Estuary, oyster farms should be sited close to river mouths so that oysters can benefit from freshwater inflows and lower salinities.

This work aimed to evaluate the whole weight (g), shell height (mm), mortality (%) and reproductive aspects (condition index and histology) of triploid (3N) Pacific oysters (Crassostrea gigas) cultivated in southern Brazil. To accomplish this, a comparative experiment was performed with a diploid (2N) control group in two cultivation sites on Santa Catarina Island: North Bay (NB) and South Bay (SB). Whole weight, height and cumulative mortality were evaluated monthly for eight months and condition index (CI) for six months. Histological analysis was performed every two weeks for four months to investigate reproductive aspects. At the end of the experiment, whole weight and height were similar for 3N and 2N oysters. However, while more growth in whole weight and height was observed in the initial phase of cultivation in NB, such growth was not detected in SB until intermediate and final grow‐out phase. At harvest, cumulative mortality in 3N oysters was similar that in 2N oysters. The results suggest that diploid and triploid oysters grown in southern Brazil have similar developmental patterns based on whole weight and height, as well as reproductive cycle. In addition, cultivation sites have more influence on growth and mortality than ploidy levels. [ABSTRACT FROM AUTHOR]

Pacific oyster Crassostrea gigas, endemic to coastal Asia, has been translocated globally throughout the past century, resulting in self‐sustaining introduced populations (naturalized). Oyster aquaculture industries in many parts of the world depend on commercially available seed (hatchery‐farmed) or naturalized/wild oysters to move onto a farm (naturalized‐farmed). It is therefore important to understand genetic variation among populations and farm types. Here, we genotype naturalized/wild populations from France, Japan, China, and most extensively in coastal British Columbia, Canada. We also genotype cultured populations from throughout the Northern Hemisphere to compare with naturalized populations. In total, 16,942 markers were identified using double‐digest RAD‐sequencing in 182 naturalized, 112 hatchery‐farmed, and 72 naturalized‐farmed oysters (n = 366). Consistent with previous studies, very low genetic differentiation was observed around Vancouver Island (mean FST = 0.0019) and low differentiation between countries in the Japan–Canada–France historical translocation lineage (France–Canada FST = 0.0024; Japan–Canada FST = 0.0060). Chinese populations were more differentiated (China–Japan FST = 0.0241). Hatchery‐propagated populations had higher interindividual relatedness suggesting family structure. Within‐population inbreeding was not detected on farms, but nucleotide diversity and polymorphism rate were lower in one farm population. Moving oysters from nature onto farms did not result in strong within‐generation selection. Private alleles at substantial frequency were identified in several hatchery populations grown in BC, suggesting nonlocal origins. Tests of selection identified outlier loci consistent with selective differences associated with domestication, in some cases consistently identified in multiple farms. Top outlier candidates were nearby genes involved in calcium signaling and calmodulin activity. Implications of potential introgression from hatchery‐farmed oysters depend on whether naturalized populations are valued as a locally adapted resource or as an introduced, invasive species. Given the value of the industry in BC and the challenges the industry faces (e.g., climate change, crop losses, biotic stressors), this remains an important question. [ABSTRACT FROM AUTHOR]

Temperature increase caused by thermal discharge from power plants promotes phytoplankton growth and frequent bloom in eutrophic subtropical waters, particularly in cold seasons. Suspension filter-feeding bivalves show size-selective grazing on phytoplankton. Thus, we hypothesized that algal bloom under thermal stimulation could be controlled and that phytoplankton community was structured by oyster farming. Here, ten cruises were conducted in two oyster farms (OFs) and control areas (CAs) adjacent to the Ninghai Power Plant in the upper section of Xiangshan Bay during 2009–2015. We found that thermal discharge induced severe winter algal blooms. Phytoplankton abundance and chlorophyll a (chla) were significantly lower (46.3% and 28.3%, respectively) in OF than in CA, indicating a high filtration efficiency by oysters and the associated biofouling assemblages. In addition, oyster farming significantly increased species richness (by 26.3%), Shannon–Wiener diversity (by 38.3%), and Pielou's evenness indices (by 28.8%) and reduced suspended solids (by 12.2%), total organic carbon (by 18.4%), dissolved inorganic nitrogen (by 1.5%), and phosphorus (by 3.7%). Furthermore, oyster farming considerably reduced (increased) micro-chla contribution (pheophytin/chla) by 34.8% (71.1%), suggesting a strong size-selective grazing on phytoplankton. Analysis of similarity revealed a significant difference in phytoplankton community composition between OF and CA. However, after the removal of culture rafts, all the abundance, chla, species diversity, dominant species, size structure, and community composition of phytoplankton showed no significant difference. Our study demonstrated that oyster farming effectively alleviated eutrophication and algal bloom and enhanced phytoplankton diversity, which provides guidance for aquaculture and ecological restoration in subtropical coastal eutrophic waters. Image 1 • Thermal discharge induced severe winter algal blooms. • Oyster farming effectively alleviated eutrophication and algal bloom. • Oyster farming significantly increased phytoplankton diversity. • Oyster farming reduced suspended solids and total organic carbon. [ABSTRACT FROM AUTHOR]

Norovirus is a significant global cause of viral gastroenteritis, with raw oyster consumption often linked to such outbreaks due to their filter-feeding in harvest waters. National water quality and depuration/relaying times are often classified using Escherichia coli , a poor proxy for norovirus levels in shellfish. The current norovirus assay is limited to only the digestive tracts of oysters, meaning the total norovirus load of an oyster may differ from reported results. These limitations motivated this work, building upon previous modelling by the authors, and considers the sequestration of norovirus into observed and cryptic (unobservable) compartments within each oyster. Results show that total norovirus levels in shellfish batches exhibit distinct peaks during the early depuration stages, with each peak's magnitude dependent on the proportion of cryptic norovirus. These results are supported by depuration trial data and other studies, where viral levels often exhibit multiphase decays. This work's significant result is that any future norovirus legislation needs to consider not only the harvest site's water classification but also the total viral load present in oysters entering the market. We show that 62 h of depuration should be undertaken before any norovirus testing is conducted on oyster samples, being the time required for cryptic viral loads to have transited into the digestive tracts where they can be detected by current assay, or have exited the oyster. • Several studies report multiphase decay of norovirus in oysters during depuration. • The model splits norovirus loads into cryptic (unobservable) and observable compartments within oysters. • Results synthesise reported multiphase decay of norovirus, with levels of cryptic norovirus dissipating after ≈ 62 hours of depuration. • To minimise food safety risks to consumers, any future legislation should assay oyster norovirus levels after 62 h of depuration to account for any cryptic norovirus levels present. [ABSTRACT FROM AUTHOR]

Ostreid oysters (the ‘true oysters’) represent a large and commercially important family of bivalve molluscs. Several species, such as the Pacific oyster (Magallana gigas), the American oyster (Crassostrea virginica), the European oyster (Ostrea edulis) and the Sydney rock oyster (Saccostrea glomerata), are currently farmed at a large scale. However a number of other species may also be suitable for commercial-scale aquaculture. One such species is the ‘black-lip oyster’, a large Saccostrea species of uncertain taxonomic affinity found in northern Australia. Here, phylogenetic analysis of the COI gene places this oyster within a clade identified in a previous study of Japanese Saccostrea species, ‘Saccostrea lineage J’. To facilitate comparisons between this oyster and the better-studied S. glomerata, de novo transcriptomes were generated from larval stages and adult tissues of both species. Patterns of orthology indicated an expansion of repetitive elements within Saccostrea genomes when compared to M. gigas and C. virginica, which may be reflected in increased evolutionary rates and/or genome sizes. The generation of high-quality transcriptomes for these two commercially relevant oysters provides a valuable resource for gene identification and comparison of molecular processes in these and other mollusc species. [ABSTRACT FROM AUTHOR]

Coastal fisheries are in decline worldwide, and aquaculture has become an increasingly popular way to meet seafood demand. While finfish aquaculture can have substantial adverse effects on coastal ecosystems due mostly to necessary feed inputs, bivalves graze on natural phytoplankton and are often considered for their positive ecosystem services. We conducted two independent studies to investigate the effects of long-line Crassostrea gigas oyster aquaculture on Zostera marina seagrass beds and associated epibiont communities in Akkeshi-ko estuary, Japan. Results from both studies yielded no evidence of an effect of oyster aquaculture on the morphology, density, or biomass of Z. marina, but significant differences were apparent in the epibiont community. Reference seagrass beds located away from aquaculture had higher seagrass epiphyte loads and higher abundances of amphipods. Conversely, seagrass beds below aquaculture lines had higher sessile polychaete biomass and higher isopod abundances. Our results suggest that the presence of oyster aquaculture may have indirect effects on seagrass by changing epibiont community composition and relative abundances of species. One proposed mechanism is that cultured oysters feed on epiphytic diatoms and epiphyte propagules before they can settle on the seagrass, which reduces epiphyte loads and influences subsequent faunal settlement. If carefully implemented and monitored, long-line oyster aquaculture may be a sustainable option to consider as bivalve aquaculture expands to meet global seafood demand, but further work is needed to fully assess and generalize the community-level effects on seagrass epibionts. [ABSTRACT FROM AUTHOR]

The abundance and distribution of microplastics within 5 sediment size classes (>5000 μm, 1000–5000 μm, 250–1000 μm, 250–0.63 μm and < 0.63 μm) were determined for 16 sites within Lambert Channel and Baynes Sound, British Columbia, Canada. This region is Canada’s premier growing area for the Pacific oyster (Crassostrea gigas). Microplastics were found at all sampling locations indicating widespread contamination of this region with these particles. Three types of microplastics were recovered: microbeads, which occurred in the greatest number (up to 25000/kg dry sediment) and microfibers and microfragments, which were much less in number compared with microbeads and occurred in similar amounts (100–300/kg dry sediment). Microbeads were recovered primarily in the < 0.63 μm and 250–0.63 μm sediment size class, whereas microfragments and microfibers were generally identified in all 5 sediment size classes. Abundance and distribution of the three types of microplastics were spatially dependent with principal component analysis (PCA) indicating that 84 percent of the variation in abundance and distribution was due to the presence of high numbers of microbeads at three locations within the study region. At these sites, microbeads expressed as a percent component of the sediment by weight was similar to key geochemical components that govern trace metal behavior and availability to benthic organisms. Microbeads have been shown to accumulate metals from the aquatic environment, hence in addition to the traditional geochemical components such as silt and organic matter, microplastics also need to be considered as a sediment component that can influence trace metal geochemistry. Our findings have shown that BC’s premier oyster growing region is highly contaminated with microplastics, notably microbeads. It would be prudent to assess the degree to which oysters from this region are ingesting microplastics. If so, it would have direct implications for Canada’s oyster farming industry with respect to the health of the oyster and the quality of product that is being farmed and sets an example for other shellfish growing regions of the world. [ABSTRACT FROM AUTHOR]

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Norovirus is a major cause of viral gastroenteritis, with shellfish consumption being identified as one potential norovirus entry point into the human population. Minimising shellfish norovirus levels is therefore important for both the consumer’s protection and the shellfish industry’s reputation. One method used to reduce microbiological risks in shellfish is depuration; however, this process also presents additional costs to industry. Providing a mechanism to estimate norovirus levels during depuration would therefore be useful to stakeholders. This paper presents a mathematical model of the depuration process and its impact on norovirus levels found in shellfish. Two fundamental stages of norovirus depuration are considered: (i) the initial distribution of norovirus loads within a shellfish population and (ii) the way in which the initial norovirus loads evolve during depuration. Realistic assumptions are made about the dynamics of norovirus during depuration, and mathematical descriptions of both stages are derived and combined into a single model. Parameters to describe the depuration effect and norovirus load values are derived from existing norovirus data obtained from U.K. harvest sites. However, obtaining population estimates of norovirus variability is time-consuming and expensive; this model addresses the issue by assuming a ‘worst case scenario’ for variability of pathogens, which is independent of mean pathogen levels. The model is then used to predict minimum depuration times required to achieve norovirus levels which fall within possible risk management levels, as well as predictions of minimum depuration times for other water-borne pathogens found in shellfish. Times for Escherichia coli predicted by the model all fall within the minimum 42 hours required for class B harvest sites, whereas minimum depuration times for norovirus and FRNA+ bacteriophage are substantially longer. Thus this study provides relevant information and tools to assist norovirus risk managers with future control strategies. [ABSTRACT FROM AUTHOR]

Like a number of countries, Ireland has set ambitious growth targets for its aquaculture sector. Economic analysis highlights that such growth has the potential to provide significant gains to the Irish economy in general, but also to peripheral rural areas in particular. However, through interviews with producers representing a significant proportion of Irish oyster production, this paper highlights the challenges faced and argues that for these growth ambitions to be realised there is a need to overcome significant regulatory, biological and financial constraints on the sector. In particular dysfunctional licensing arrangements are a major constraint on the development of the sector. It is argued that licensing reform is a necessary but not sufficient condition for a thriving oyster industry and that a more holistic view of the industry needs to be taken. [ABSTRACT FROM AUTHOR]

Purpose - To determine the sociocultural characteristics and unravel the ethnomathematics in Panaeaba or oyster farming of the fourteen Manugtaeaba (oyster farmer) purposively chosen as informants and paired the mathematical concepts and principles found in Panaeaba to K12 Mathematics. Method - This focused ethnographic study was generally governed by the epistemological umbrella of constructionism and symbolic interactionism as its interpretive approach for the thematic, ethnomathematical and document analyses. Data gathered through ethnographic interview and observation and collection of artifacts. Findings - Ethnomathematics along Numbers and Number Sense, Algebra, Measurement, and Geometry were used in Panaeaba. The Ethnomathematical Knowledge, Practices and Skills (EKPS) on numbers and number sense used by Manugtaeaba were rational numbers, counting, equality and inequality, estimation, fundamental, ratio and proportion. For EKPS along algebra includes the parabola, relations, and functions in line with size or area of oyster shell, density of spat collection, buoyancy, and navigational speed. Also, the EKPS along measurement includes how farmers used standard and alternative measurement on area, volume, distance, height, length, and time in oyster farming. The EKPS along geometry includes angles, and parallelism. These EKPS are influenced by the sociocultural characteristics in terms of Manugtaeaba's beliefs and attitude towards family and work. Significance - From the unraveled EKPS in Panaeaba, the researcher came up with the matrix of the mathematical concepts and principles and K-12 learning competencies known as TALAMATH. From this TALAMATH (Teaching A Localized and Actualized Mathematics), lesson exemplars that can be used in the teaching of mathematics and will serve as guide for the development of instructional materials contextualized in oyster farming were made. [ABSTRACT FROM AUTHOR]

Oysters represent an important portion of the world’s total aquaculture production. In recent years, in Italy, oyster farming has progressively increased its role in the economic growth of the aquaculture sector and still has great potential for growth. As in any other production, oyster farming generates environmental impacts over an oyster’s life cycle, due to material, energy, fuel, and water use. The aim of this work was to carry out a cradle-to-gate life cycle assessment (LCA) of 1 kg of fresh oysters of commercial size produced in the Po delta area, northern Italy. Two scenarios were considered. The current scenario provides for oyster seed purchasing from France and transport to Italy, whereas the alternative scenario includes in situ seed production in order to realize a complete local and traceable supply chain. Eco-indicator® 99-H and ReCiPe® midpoint (H) v.1.12 were used to perform the impact assessments. The overall impacts of the two scenarios were very similar and indicated that the main hotspots were the fattening and prefattening phases of farming, which were common in both scenarios. Focusing the analysis on the first stages, transport from France had a greater impact than did local seed production, emphasizing the importance of a short supply chain in aquaculture production.

Single nucleotide polymorphisms (SNPs) are widely used in genetics and genomics research. The Pacific oyster (Crassostrea gigas) is an economically and ecologically important marine bivalve, and it possesses one of the highest levels of genomic DNA variation among animal species. Pacific oyster SNPs have been extensively investigated; however, the mechanisms by which these SNPs may be used in a high-throughput, transferable, and economical manner remain to be elucidated. Here, we constructed an oyster 190K SNP array using Affymetrix Axiom genotyping technology. We designed 190,420 SNPs on the chip; these SNPs were selected from 54 million SNPs identified through re-sequencing of 472 Pacific oysters collected in China, Japan, Korea, and Canada. Our genotyping results indicated that 133,984 (70.4%) SNPs were polymorphic and successfully converted on the chip. The SNPs were distributed evenly throughout the oyster genome, located in 3,595 scaffolds with a length of ~509.4 million; the average interval spacing was 4,210 bp. In addition, 111,158 SNPs were distributed in 21,050 coding genes, with an average of 5.3 SNPs per gene. In comparison with genotypes obtained through re-sequencing, ~69% of the converted SNPs had a concordance rate of >0.971; the mean concordance rate was 0.966. Evaluation based on genotypes of full-sib family individuals revealed that the average genotyping accuracy rate was 0.975. Carrying 133 K polymorphic SNPs, our oyster 190K SNP array is the first commercially available high-density SNP chip for mollusks, with the highest throughput. It represents a valuable tool for oyster genome-wide association studies, fine linkage mapping, and population genetics. [ABSTRACT FROM AUTHOR]